Conservation Scholars: Daniel Simberloff

30102008

This series on ConservationBytes.com takes a page out of our book Tropical Conservation Biology (Sodhi, Brook & Bradshaw) – therein we produced a series of ‘Spotlights’ describing the contributions of great thinkers to conservation science. Each highlight of a Conservation Scholar includes a small biography, a list of major scientific publications and a Q & A on the person’s particular area of expertise.

As a child in rural Pennsylvania, I was fascinated by nature, collecting insects from age five and keeping insects, turtles, and fish as pets. This idyll crashed to a halt at age 11 when we moved to an industrial suburb of New York City. I attended Harvard College, where I became excited by maths and majored in it. My junior year, while enjoying a non-majors biology course and realising that I wasn’t so enthusiastic about a maths career, I consulted a biology department advisor about postgraduate work. Frank Carpenter, an insect palaeontologist, astounded me by saying I could go to graduate school in biology with a little coursework in my final year. He also directed me to Ed Wilson as a potential graduate advisor. Ed introduced me to ecology and argued that maths is crucial to the maturation of ecology. He taught me an enormous amount of biology and encouraged me in a great doctoral dissertation project, testing the theory of island biogeography that he had recently propounded with Robert MacArthur. We collaborated in fumigating small Florida mangrove islands and studying their recolonisation by insects. Bill Bossert taught me about computers well before everyone knew about them. Beginning with my doctorate, my main interest has been how different species fit (or do not fit) together in communities, and this interest led to research in conservation issues, most notably on refuge design and impacts and management of introduced species, as well as more academic aspects of ecology, like the role of inter-specific competition. As a faculty member at Florida State University and now the University of Tennessee, I have learnt an enormous amount from excellent colleagues, postgraduate students, and post-doctoral fellows. I also quickly interacted with policy makers and non-governmental organisations on conservation issues, first at the local and state levels, then nationally. My most important advice to prospective conservation biology students is to interact with challenging people doing interesting research and to engage in local conservation issues.

1. What are the defining characteristics of an alien organism that make it ‘invasive’?

An invasive introduced species is one that spreads into more or less natural ecosystems and thrives there, affecting native species.

2. Is there merit in the idea that tropical ecosystems are more resistant to invasion due to their species richness and complexity?

I don’t believe either premise, that tropical ecosystems are particularly resistant to invasion or that complex ecosystems with many species are particularly resistant to invasion. There are many invasions into tropical ecosystems, including species-rich ones, and extensive research fails to support Elton’s hypothesis that biological invasions are greatly facilitated by low native species richness. Any ecosystem is invasible by the right invader.

3. How common are ‘invasional meltdowns’, and what are the best tropical examples?

It is too early to know just how common invasional meltdowns are, but every year more cases are suggested, and some are buttressed by careful study. An important tropical example is the near destruction of the forest ecosystems of Christmas Island (Indian Ocean) by the introduced yellow crazy ant, whose population explosion was facilitated by later invasions of scale insects that produced a honeydew fed on by the ants. The ants devastated populations of the keystone species, the famed red land crab, and their impact on the forest was exacerbated by a plant pathogen (a sooty mould). See O’Dowd D. J., Green P. T. & Lake P. S. (2003). Invasional ‘meltdown’ on an oceanic island. Ecology Letters 6, 812-817.

The best defence against invasive introduced species is to avoid introducing them in the first place, by having more stringent regulations on movement of goods and by better inspections of luggage and cargo. The second line of defence is an effective early warning/rapid response system, which requires both ongoing monitoring and the institutional and legal mechanisms to act quickly when an invasion is discovered. Many introduced species have been eradicated before they spread too far, and many more could have been eradicated if a good early warning/rapid response system was in place. Once a species is established, biological, chemical, and mechanical control, genetic intervention, and ecosystem management all have roles to play in particular cases in maintaining invader populations at low levels. However, ecosystem management and genetic intervention, though widely discussed, have so far rarely been used to deal with introduced species, particularly in natural environments. By contrast, there are many successful uses of biological, chemical, and mechanical control. It is nonetheless important to recognize that the great majority of biological control projects do not control the target pest, that species introduced for biological control can and sometimes do attack non-target native species, and that once a biological control agent is well-established, it is difficult if not impossible to eradicate it, even if it turns out to be problematic. The latter feature contrasts with mechanical and chemical control, which can simply be terminated if they are not working as planned. For this reason, I feel it is important to consider all possible means of dealing with introduced pests, and to take account of the irreversibility and historically low success rate of biological control.

5. Do large-scale, co-ordinated efforts like the United Nations Global Invasive Species Program (GISP) offer the best means of addressing the problems of alien species?

Large international efforts, such as GISP, are important tools in dealing with introduced species. They can particularly aid in slowing down the rate at which non-native species arrive and in publicizing the problem and educating people about how to deal with particular invasions (as GISP has done). However, the most important response to introduced species will always be the efforts that each nation will mount against invaders that breach its borders, in terms of early warning/rapid response, attempted eradication, and effective maintenance management.

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[…] Conservation Scholars: Daniel SimberloffEd introduced me to ecology and argued that maths is crucial to the maturation of ecology. He taught me an enormous amount of biology and encouraged me in a great doctoral dissertation project, testing the theory of island biogeography … […]